The cause was found to be carelessness of the driver of the autotrain (also called a railmotor) who was running too fast for conditions.
Fog, unsafe railway rules, and possible distraction from passengers all may have contributed to the accident.
[1] When this railway implemented the automatic signals on this line, they also introduced a unique "Stop and Proceed" rule.
This allowed the driver of a train to proceed cautiously into an occupied block after waiting two minutes and sounding the whistle, but without communicating with a signalman.
This was a traditional passenger train consisting of 13 six-wheeled coaches, pulled by 4-6-4 steam locomotive Number 25.
This so-called railmotor was three coaches being pushed by a 2-4-2 tank locomotive, Number 5, which was running bunker first.
[2] Rescuers came from the neighbourhood of the crash, including many workers from the nearby Harland and Wolff Shipyard.
The driver of the 7:40, Isaac McQuillan, was charged with manslaughter in April 1945 for the death of a passenger: Samuel Wilson.
During the trial, an expert witness for the defence said the "Stop and Proceed" rule was unheard of in Britain and placed an unfair burden on the driver.
Another defence witness, a civil engineer, said the police tests of the braking system found it to be extremely inefficient.
"[10] In February 1947, the Railway tried to have its liability in the case of William Redpath of Bangor reduced by the amount of monies received by the victim from charities.
After a protest from a member of the public, Mr. Duncan explained that the purpose of the hearing was to learn what could be changed on the railways to prevent future accidents and was not to fix blame.
The signalman at the interlocking had tried to clear the signal to allow the train to continue, but it was stuck in the danger position due to wet or frosty weather causing the mechanism to stick.
[2] The report commented on and criticised the fact that the signal system was in need of modernization and that the rules that permitted this accident to occur should be made more stringent.
The driver of the 7:40 was solely blamed for the accident for running at too high a speed for the conditions and the signals received.
The driver was also criticised for the possibility of allowing passengers in the crowded train to stand in his compartment that may have provided a distraction.
[2] The job of telling the families of the victims about the accident and the loss of their loved ones fell to the Station Master of Bangor with his assistant, who were accompanied by a police officer.
[15] The drive raised some £20,000, which is considered extraordinary for the time given, the hardships that the area and the entire British Commonwealth had been through with the Second World War.
[1] Push-pull trains were withdrawn from service; the Stop and Proceed rule was removed, and lineside telephones were installed after the accident.